Tech: 2015 Mustang Clutch Install

Twice and Nice

Lethal Performance harnesses the power of its supercharged S550 with a McLeod RXT

By Steve Turner
Photos courtesy of Lethal Performance

Modern performance cars are horsepower marvels. With bolt-on modifications these vehicles can produce stratospheric performance while retaining stock-like driveability. In the case of Lethal Performance’s 2015 Mustang, we have seen it escalate quickly from bolt-ons to nitrous to a Whipple supercharger. With that last addition it’s making almost double the rear-wheel horsepower it did from the factory.

Here’s a breakdown of how the McLeod Racing RXT twin-disc clutch goes together. A steel disc is sandwiched between the two friction discs, which are engaged by a single pressure plate. The system is available with either a steel (PN MCL-6932-25+463458; $1,366.02) or aluminum (PN MCL-6932-25+563408; $1,409.86) flywheel depending on your application. The kits come complete with ARP hardware and a clutch-alignment tool.

Packing that potent punch under the hood is one thing, but passing it through the stock drivetrain is another. Team Lethal has plans to hit the drag strip hard with its supercharged ’Stang, so the stock clutch would certainly be on borrowed time when wedged between Whipple power and a sticky drag strip. Rather than waiting for the factory unit to fail, the Lethal crew opted to head that problem off at the pass.

The trick to keeping these big-power machines streetable is balancing performance and comfort. In order to ensure the clutch could live behind 700 rear-wheel horsepower and not turn the clutch pedal into a leg press, the company chose one of McLeod Racing’s RXT Street Twin clutch systems.

Increasing the clamping force of a clutch is often achieved by installing more aggressive surfaces on the discs or ramping up the pressure applied. Those methods obviously will hurt the driveabilty of the clutch, which is fine for a race car, but not something you want in your high-powered street car.

Jesse Guajardo of Power by the Hour gets started by disconnected the American Racing Headers’ exhaust system mid-pipe to clear the path for removing the transmission.

“We chose to use the McLeod RXT clutch on our 2015 as we’ve used McLeod clutches in all of our project cars with great success. You really can’t beat being able to hold 1000 rear-wheel horsepower and still have stock like driveability,” Jared Rosen of Lethal Performance explained. “Most of the other clutches on the market that are designed to hold that type of power have a very heavy pedal feel and chatter like crazy, not McLeod. That is exactly why it’s our best-selling clutch, and has been for the last several years.”

You can also increase the grip of the clutch by increasing the surface area of the clutch discs. This is how a twin-disc unit works its magic. By sharing the torque load between two discs, these twin-disc clutches offer massive clamping capacity while delivering a buttery smooth pedal engagement.

Next, he removes the D.S.S. Racing driveshaft. If you’ve been following along with our stories on this project, you’ve seen how the exhaust and driveshaft went in.

“Just like any of the other RST/RXT clutches I’ve driven, this one has the exact same stock-like feel to it,” he said. “When I asked Ken Bjonnes of Lund Racing how he thought the clutch felt as he has been tuning the car this past week he said, ‘I didn’t even know you changed the clutch in it.’ That pretty much sums it up.”

Interestingly, Lethal is working with McLeod to test a new disc friction material that may work even better on potent street machines like the Lethal 2015 Mustang.

“The clutch that we’re testing for McLeod is expected to perform even better than the RXT with more holding power and same excellent driveability characteristics,” Jared said. “This is due to the newly designed material being used on the clutch discs. Although it may look exactly like the RXT using the RXT’s pressure plate and flywheel it’s the new material on the discs that makes it different.”

Of course, a twin-disc clutch like the RXT does require a bit more setup to install, but the results are definitely worth it. If you plan on installing one in your car and you need a video primer, you can check out McLeod Racing’s install video here…

To get the specifics of the installation on a new Mustang, we tuned in as the Jesse Guajardo at Power by the Hour in Boynton Beach, Florida, installed the RXT in the Lethal S550.

With the Getrag MT-82 supported on a trans jack, Jesse unbolts the starter and the bellhousing.After freeing the fasteners, Jesse drops the stock six-speed out of the car.Sparing it from a fate of handling 700 rear-wheel horsepower at the drag strip, Jesse removes the stock clutch.They say you can’t judge a book by its cover, but in the case of the McLeod RXT, it’s hard not to take a look at it and say it is a far more serious unit than the stocker (left). Clearly, the RXT is more serious, as it is designed to corral up to 1,000 horsepower. You’ll need to disassemble the RXT as outlined in the instructions, setting aside pressure plate nuts for later use.Since the McLeod RXT comes with its own flywheel, Jesse unbolts the factory flywheel and removes it. Take a good look at the pilot bearing. If it is in good shape, you can stick with it, but if it’s damaged, you’ll need to remove it will a puller and tap in a fresh bearing.After cleaning the flywheel to ensure that it is free of oil, Jesse installs the McLeod unit on the crank of the Lethal GT’s Coyote engine and torques the fasteners to the factory spec.Using the supplied alignment tool Jesse first installed the “bottom” clutch disc followed by the floater disc, torquing its 5/16-inch fasteners to 25 lb-ft. The bottom disc should spin freely at this point. If it doesn’t, you need to troubleshoot things.Using the alignment tool, Jesse follows up the floater install by installing the top clutch disc. With it in place he bolts on the pressure plate, paying close attention to the orientation of the alignment straps. First install the six flat washers, then the six lock washers and finally the six nuts. Start them finger tight, then torque them in a star pattern to 25 lb-ft. Final torque them till the diaphragm fingers start pulling toward the flywheel; This should be at around 35 lb-ft.Make sure all the fingers of the diaphragm are below the rear surface of the pressure plate. If you aren’t sure, use a straight edge. You can then reinstall the throw-out bearing, transmission, driveshaft, exhaust, and, in this case, the BMR driveshaft safety loop. Once the car is back together, you’ll need to break-in the clutch with about 500 street miles, driving with the traction control off.